Manufacturing method of the display device

ABSTRACT

A display device includes a display region arranged above a substrate, a first light emitting element emitting light of a first color, a second light emitting element emitting light of a second color, and a third light emitting element emitting light of a third color arranged in the display region, and a first optical path length adjustment film, a second optical path length adjustment film, and a third optical path length adjustment film in the display region.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/730,106, filed on Dec. 30, 2019, which, in turn, is a continuation ofU.S. patent application Ser. No. 15/916,369 (now U.S. Pat. No.10,559,781), filed on Mar. 9, 2018. Further, this application is basedupon and claims the benefit of priority from the prior Japanese PatentApplication No. 2017-076070, filed on Apr. 6, 2017, the entire contentsof which are incorporated herein by reference into this application.

FIELD

One embodiment of the present invention is related to an organic ELdisplay device and a method of manufacturing the organic EL displaydevice.

BACKGROUND

Conventionally, as a display device, an organic EL display device(Organic Electroluminescence Display) using an organicelectroluminescence material (organic EL material) in a light emittingelement (organic EL element) of a display part is known. Unlike a liquidcrystal display device or the like, the organic EL display device is aso-called self-light emitting type display device which realizes adisplay by causing the organic EL material to emit light.

In a top emission type organic EL display device, a microcavitystructure which utilizes a resonance effect of light between areflection electrode as a pixel electrode and a semitransparentelectrode as a counter electrode is generally used. In the microcavitystructure, EL spectrum peak wavelengths of each color of red, green, andblue (RGB) are made to coincide with an optical path length between thepixel electrode and the counter electrode, and the film thickness of anorganic layer between the pixel electrode and the counter electrode ischanged in order to extract the strongest light from each color. In thisway, it is possible to resonate and emphasize only light having awavelength which coincides with the optical path length, and it ispossible to weaken light having a wavelength which has a misalignedoptical path length. Therefore, the spectrum of light extracted to theexterior becomes high intensity, and luminosity and color purity areimproved.

In recent years, a structure in which a film for adjusting an opticalpath length is also arranged above the semitransparent electrode hasbeen examined in order to further improve the efficiency of a displaydevice. For example, a structure has been disclosed in which a highrefractive index film and a low refractive index film are alternatelystacked above a semitransparent electrode (for example, Japanese LaidOpen Patent publication No. 2014-56666).

SUMMARY

A display device according to and embodiment of the present inventionincludes a display region arranged above a substrate, a first lightemitting element emitting light of a first color, a second lightemitting element emitting light of a second color, and a third lightemitting element emitting light of a third color arranged in the displayregion, and a first optical path length adjustment film, a secondoptical path length adjustment film, and a third optical path lengthadjustment film in the display region. The first optical path lengthadjustment film has a first region overlapping the first light emittingelement, the second light emitting element and the third light emittingelement, the second optical path length adjustment film has a secondregion not overlapping the third light emitting element, and overlappingthe first light emitting element and the second light emitting element,and the third optical path length adjustment film has a third region notoverlapping the second light emitting element, and overlapping the firstlight emitting element and the third light emitting element.

A display device according to and embodiment of the present inventionincludes a display region arranged above a substrate, a first lightemitting element emitting light of a first color, a second lightemitting element emitting light of a second color, a third lightemitting element emitting light of the second color and a fourth lightemitting element emitting light of a third color arranged in the displayregion; and a first optical path length adjustment film, a secondoptical path length adjustment film, and a third optical path lengthadjustment film in the display region. The first optical path lengthadjustment film has a first region overlapping the first light emittingelement, the second light emitting element, the third light emittingelement and the fourth light emitting element, the second optical pathlength adjustment film has a second region not overlapping the thirdlight emitting element and the fourth light emitting element, andoverlapping the first light emitting element and the second lightemitting element, and the third optical path length adjustment film hasa third region not overlapping the second light emitting element and thefourth light emitting element, and overlapping the first light emittingelement and the third light emitting element.

A manufacturing method according to and embodiment of the presentinvention includes, forming a first light emitting element emittinglight of a first color, a second light emitting element emitting lightof a second color, and a third light emitting element emitting light ofa third color above a substrate, forming a first optical path lengthadjustment film above the first light emitting element, the second lightemitting element and the third light emitting element, forming a secondoptical path length adjustment film above the first light emittingelement and the second light emitting element, the second optical pathlength adjustment film serving as an outer side of the third lightemitting element, and forming a third optical path length adjustmentfilm above the first light emitting element and the third light emittingelement, the third optical path length adjustment film serving as anouter side of the second light emitting element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a structure of a display device related toone embodiment of the present invention;

FIG. 2 is a cross-sectional view cut along the line A1-A2 of the displaydevice shown in FIG. 1;

FIG. 3 is a planar expanded view of a part of a display region of adisplay device related to one embodiment of the present invention;

FIG. 4 is a planar expanded view of a part of a display region of adisplay device related to one embodiment of the present invention;

FIG. 5 is a planar expanded view of a part of a display region of adisplay device related to one embodiment of the present invention;

FIG. 6 is a planar expanded view of a part of a display region of adisplay device related to one embodiment of the present invention;

FIG. 7 is a planar expanded view of a part of a display region of adisplay device related to one embodiment of the present invention;

FIG. 8 is of a cross-sectional view cut along the line C1-C2 of thedisplay device shown in FIG. 1;

FIG. 9 is a planar expanded view of a part of a display region of adisplay device related to one embodiment of the present invention;

FIG. 10 is a cross-sectional view for explaining a manufacturing methodof a display device related to one embodiment of the present invention;

FIG. 11 is a cross-sectional view for explaining a manufacturing methodof a display device related to one embodiment of the present invention;

FIG. 12 is a cross-sectional view for explaining a manufacturing methodof a display device related to one embodiment of the present invention;and

FIG. 13 is a cross-sectional view for explaining a manufacturing methodof a display device related to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention are explained below whilereferring to the drawings. However, it is possible to perform thepresent invention using various different forms, and the presentinvention should not be limited to the content described in theembodiments exemplified herein. In addition, although the width,thickness and shape of each component are shown schematically comparedto their actual form in order to better clarify explanation, thedrawings are merely an example and should not limit an interpretation ofthe present invention. Furthermore, in the specification and eachdrawing, the same reference symbols are attached to similar elements andelements that have been mentioned in previous drawings, and therefore adetailed explanation may be omitted where appropriate.

In the present specification and claims, when a plurality of films isformed by processing one film, the films may have functions or rulesdifferent from each other. However, the films each originate from a filmformed as the same layer in the same process and has the same layerstructure and the same material. Therefore, the films are defined asfilms existing in the same layer.

Furthermore, in the present specification, expressions such as “above”and “below” when explaining the drawings express a relative positionalrelationship between a structured body in question and other structuredbodies. In the present specification, in a side surface view, adirection facing a bank from an insulating surface described later isdefined as “upper” and the reverse direction is defined as “below”. Inthe present specification and the scope of the patent claims, in thecase of simply describing “above” when expressing a state in which otherstructured bodies are arranged above a certain structure body, as longas there is no particular limitation, this includes both the case whereother structured bodies are arranged directly above in contact with acertain body, and a case where other structured bodies are arrangedabove a certain body interposed by another structured body.

Furthermore, the ordinals such as “first”, “second” and “third” in thepresent specification are used only for simplifying explanation andshould not be interpreted in a limited manner.

First Embodiment

In the present embodiment, a display device according to one embodimentof the present invention is explained referring to FIG. 1 and FIG. 2.

Structure of Display Device

FIG. 1 is a schematic view showing a structure of a display device 100according to one embodiment of the present invention, and shows aschematic structure in the case when the display device 100 is seen in aplanar view. In the present specification and the like, a state in whichthe display device 100 is viewed from a direction perpendicular to thescreen (display region) is referred to as “planar view”.

As shown in FIG. 1, the display device 100 includes a display region103, a scanning line drive circuit 104, and a driver IC 106 arranged onan insulating surface. In addition, a counter substrate 102 is arrangedabove the display region 103 and the scanning line drive circuit 104. Aplurality of scanning lines 105 is connected to the scanning line drivecircuit 104 in a direction x. The driver IC 106 functions as a controlpart which provides signals to the scanning line drive circuit 104. Adata line drive circuit is incorporated in the driver IC 106.Furthermore, a plurality of data lines is connected to the driver IC 106in a direction y orthogonal to the direction x, but these are omitted inFIG. 1. In addition, although the driver IC 106 is externally arrangedon a flexible printed substrate 108 by a COF (Chip on Film) method, itmay also be arranged on the first substrate 101. The flexible printedsubstrate 108 is connected to terminals 107 arranged in a peripheryregion 110.

Here, the insulating surface is a surface of the first substrate 101.The first substrate 101 supports each layer forming a transistor or alight emitting element and the like arranged on the surface of the firstsubstrate 101. A glass substrate or a semiconductor substrate and thelike can be used as the first substrate 101. In addition, a foldablesubstrate may be used as the first substrate 101. An organic resinmaterial such as polyimide, acrylic, epoxy, polyethylene terephthalateor the like can be used as the first substrate 101. In addition, it ispreferred to use a material that transmits light as the first substrate101. In addition, the same substrate as the first substrate 101 can beused as the counter substrate 102.

A plurality of pixels are arranged in a matrix shape so as to be alongdirections (for example, x direction and y direction orthogonal to eachother) which intersect each other in the display region 103 shown inFIG. 1. Each of the plurality of pixels has either a first lightemitting element emitting light of a first color, a second lightemitting element emitting light of a second color and a third lightemitting element emitting light of a third color. In the presentspecification, in the case of a display panel which uses light emittingelements of R (red), G (green), and B (blue), one pixel refers to aregion having a light emitting element which emits one of three colors.The color emitted by the light emitting element is not limited to threecolors, and may be four or more colors. In FIG. 1, the case of a stripearrangement in which each of a plurality of red pixels 109R, a pluralityof green pixels 109G and a plurality of blue pixels 109B are arrangedalong first direction (y direction) of the display region 103 isexplained.

Each of the pixels 109R, 109G and 109B includes a pixel electrodedescribed later, and a light emitting element comprised from a part ofthe pixel electrode (anode), an organic layer (light emitting part)including a light emitting layer stacked above the pixel electrode, anda cathode. In FIG. 1, the parts shown as the pixels 109R, 109G and 109Bare light emitting regions of a light emitting element. In FIG. 1,although the area of the light emitting region of each pixel is shown tobe the same, one embodiment of the present invention is not limitedthereto, and the area of the light emitting region may be different foreach color.

A video signal is provided to the pixels 109R, 109G 109B from the dataline drive circuit incorporated in the driver IC 106. According to thesedata signals, transistors which are electrically connected to the pixelelectrodes arranged in the pixels 109R, 109G and 109B are driven todisplay a screen according to the image data. Typically, it is possibleto use a thin film transistor (TFT) as the transistor. However, it isnot limited to a thin film transistor and any element may be used aslong as it has a current control function.

A half mirror formed by stacking layers having different refractiveindices is arranged above the light emitting element of each pixel. Thehalf mirror forms a resonator together with a pixel electrode havingreflective properties. In the present embodiment, a case where anoptical path length adjusting film having a high refractive index and anoptical path length adjusting film having a low refractive index arearranged above a light emitting element is explained.

The optical path length adjusting film having the high refractive indexand the optical path length adjusting film having the low refractiveindex have different optimum film thicknesses depending on each color.For example, in the optical path length adjustment film having the highrefractive index, when the film thickness in the pixel 109R is T1, thefilm thickness in the pixel 109G is T2, and the film thickness in thepixel 109B is T3, it is preferred that the film thickness relationshipT1>T2>T3 is satisfied. However, when each optical path length adjustingfilm is formed with a common film thickness without using a fine mask,it is impossible to maximize the light emitting efficiency for eachlight emitting element of each color. In addition, when each opticalpath length adjusting film is formed with a common film thickness sothat the light emitting efficiency of a certain color is maximized, thelight emitting efficiency of the other colors decreases.

Therefore, in order to maximize the light emitting efficiency of thelight emitting element of each color, it is desirable to pattern theoptical path length adjusting film to an optimum film thickness for alight emitting element of each color. However, as the display devicebecomes higher in definition, patterning the optical path lengthadjusting film for each light emitting element of each color becomesdifficult.

In the present embodiment, the optical path length adjusting film havingthe high refractive index is divided into three patterns and isstructured so that they overlap on light emitting elements of aplurality of colors. FIG. 1 shows a structure in which the optical pathlength adjusting film having the high refractive index is divided intothree patterns, an optical path length adjusting film 151, an opticalpath length adjusting film 152 and an optical path length adjusting film153.

The optical path length adjusting film 151 is arranged in the pixels109R, 109G and 109B as the first pattern. FIG. 1 shows an example inwhich the optical path length adjusting film 151 is arranged over theentire surface of the display region 103 and is also arrangedoverlapping the scanning line drive circuit 104. Furthermore, thepresent invention is not limited to this structure, and the optical pathlength adjusting film 151 may be arranged at least over the entiresurface of the display region 103.

The optical path length adjusting film 152 is arranged above the opticalpath length adjusting film 151 as the second pattern. In addition, theoptical path length adjusting film 152 is arranged in the pixel 109R andthe pixel 109G. In addition, the longitudinal direction of the opticalpath length adjusting film 152 is orthogonal to a first direction (xdirection) in which a scanning line 105 connected to the scanning linedrive circuit 104 extends.

The optical path length adjusting film 153 is arranged above the opticalpath length adjusting film 151 and the optical path length adjustingfilm 152 as a third pattern. In addition, the optical path lengthadjusting film 153 is arranged in the pixel 109R adjacent to the pixel109B. The longitudinal direction of the optical path length adjustingfilm 153 is orthogonal to the first direction in which the scanning line105 connected to the scanning line drive circuit 104 extends.

By arranging the optical path length adjusting film 151, the opticalpath length adjusting film 152 and the optical path length adjustingfilm 153 as described above, in the red pixel 109R, the optical pathlength adjusting film 151, the optical path length adjusting film 152and the optical path length adjustment film 153 are stacked. Inaddition, in the green pixel 109G, the optical path length adjustingfilm 151 and the optical path length adjusting film 152 are stacked. Inaddition, in the blue pixel 109B, the optical path length adjusting film151 and the optical path length adjusting film 153 are stacked.

Here, in the red pixel 109R, the total thickness of the film thicknessof the optical path length adjusting film 151, the film thickness of theoptical path length adjusting film 152 and the film thickness of theoptical path length adjusting film 153 is t1. In addition, the totalthickness of the film thickness of the optical path length adjustingfilm 151 and the film thickness of the optical path length adjustingfilm 152 in the green pixel 109G is t2. In addition, the total filmthickness of the optical path length adjusting film 151 and the filmthickness of the optical path length adjusting film 153 in the bluepixel 109B is t3. It is preferable to set the film thicknesses of theoptical path length adjusting films 151, 152, 153 so that therelationship between the film thickness t1, the film thickness t2 andthe film thickness t3 satisfies t1>t2>t3.

The film thickness of the optical path length adjusting film 151 is setto 20 nm or more and 40 nm or less, the film thickness of the opticalpath length adjustment film 152 is set to 50 nm or more and 70 nm orless, and the film thickness of the optical path length adjustment film153 is set to 20 nm or more and 40 nm or less. In the presentembodiment, the film thickness of the optical path length adjusting film152 is made thicker than the each of the film thicknesses of the opticalpath length adjusting film 151 and the optical path length adjustingfilm 153. The film thickness of the optical path length adjusting film151 is set the same as the film thickness of the optical path lengthadjusting film 153.

As explained above, a structure is provided in which the optical pathlength adjusting film having the high refractive index is divided intothree patterns and is arranged on light emitting elements of a pluralityof colors. In this way, even if the optical path length adjusting filmhaving the high refractive index is divided into three patterns for eachcolor so as not to have an optimum film thickness for a light emittingelement of each color, it is possible to arrange the optical path lengthadjusting film so that it has the optimum film thickness a lightemitting element of each color. It is possible to obtain a displaydevice with light emitting elements of each color with improved lightemitting efficiency.

Furthermore, although not shown in the drawing, the optical path lengthadjusting film having the low refractive index may be divided into threepatterns and arranged above the light emitting elements of a pluralityof colors the same as the optical path length adjusting film having thehigh refractive index.

Structure of Light Emitting Element and Optical Path Length AdjustingFilm

Next, the structure of a cross section of a light emitting element andthe optical path length adjusting film is explained while referring toFIG. 2. FIG. 2 shows a cross-sectional view of the pixel 109R, pixel109G and pixel 109B. The pixel 109R includes a light emitting element130R, the pixel 109G includes a light emitting element 130G, and thepixel 109B includes a light emitting element 130B. In addition, thelight emitting element 130R includes an organic layer 127R, the lightemitting element 130G includes an organic layer 127G, and the lightemitting element 130B includes an organic layer 127B.

First, the structures of the light emitting element 130R, the lightemitting element 130G and the light emitting element 130B are explainedin detail. Each of the pixels 109R, 109G and 109B is arranged with apixel electrode. The pixel electrode is arranged for each pixel. Inaddition, in FIG. 3, the pixel electrodes are shown as pixel electrodes125 a and 125 b. The pixel electrode 125 a is formed from a materialhaving reflective properties and the pixel electrode 125 b is formedfrom a material having translucency.

A hole injection layer 161 is arranged above the pixel electrode 125 b.The hole injection layer 161 is arranged in common for the pixels 109R,109G and 109B.

A hole transport layer is arranged above the hole injection layer 161.It is also preferred to form the hole transport layer into threepatterns. The hole transport layer 162 a is arranged in common to thepixels 109R, 109G and 109B as the first pattern. In addition, as thesecond pattern, the hole transporting layer 162 b is arranged in aregion where the pixel 109R is formed, and as the third pattern, thehole transporting layer 162 c is arranged in a region where the pixel109G is formed. In this way, in the hole transport layer, it is possibleto adjust the optical path length by arranging it with a changed filmthickness for each color of the light emitting element. In this way,only light having a wavelength matching the optical path length isresonated and emphasized and it is possible to weaken the light with awavelength whose optical path length is shifted. Therefore, the spectrumof light extracted to the exterior becomes high intensity and luminanceand color purity are improved. Here, the hole transporting layer of thepixel 109R is the thickest, the next thickest is the hole transportinglayer of the pixel 109G, and the thinnest is the hole transporting layerof the pixel 109B.

An electron blocking layer 163 is arranged above the hole transportinglayer. The electron blocking layer 163 is arranged in common with thepixels 109R, 109G and 109B.

Light emitting layers 164R, 164G and 164B are arranged above theelectron blocking layer 163. The light emitting layer 164R is arrangedin the pixel 109R, the light emitting layer 164G is arranged in thepixel 109G, and the light emitting layer 164B is arranged in the pixel109B.

A hole blocking layer 165 is arranged above the light emitting layers164R, 164G and 164B. An electron transporting layer 166 is arrangedabove the hole blocking layer 165. An electron injecting layer 167 isarranged above the electron transporting layer 166. The hole blockinglayer 165, the electron transport layer 166 and the electron injectionlayer 167 are arranged in common with the pixels 109R, 109G and 109B.

A counter electrode 128 is arranged above the electron injection layer167. The counter electrode 128 is arranged in common with the pixels109R, 109G and 109B.

In this way, it is possible to form each of the light emitting elements130R, 130G and 130B by stacking from the pixel electrode 125 a to thecounter electrode 128.

In addition, the optical path length adjusting film having the highrefractive index and the optical path length adjusting film having thelow refractive index are stacked above the light emitting elements 130R,130G and 130B. The optical path length adjusting film having the highrefractive index is formed by the optical path length adjusting film151, the optical path length adjusting film 152 and the optical pathlength adjusting film 153. That is, the optical path length adjustingfilms 151, 152 and 153 are made of the same material having the samerefractive index.

The optical path length adjusting film 151 has a region which overlapsthe light emitting elements 130R, 130G and 130B. In addition, theoptical path length adjusting film 152 is arranged above the opticalpath length adjusting film 151, and has a region which overlaps thelight emitting element 130R and the light emitting element 130B. Inaddition, the optical path length adjusting film 153 is arranged abovethe optical path length adjusting film 151 and the optical path lengthadjusting film 152, and has a region which overlaps the light emittingelement 130R and the light emitting element 130B.

In addition, an optical path length adjusting film 154 having the lowrefractive index is arranged above the optical path length adjustingfilms 151, 152 and 153 which have the high refractive index. The opticalpath length adjusting film 154 is arranged in common with the pixels109R, 109G and 109B.

Although an example in which the optical path length adjusting films151, 152 and 153 having the high refractive index are stacked in thisorder is shown in FIG. 2, an embodiment of the present invention is notlimited to this example. The stacking order of the optical path lengthadjusting films 151, 152 and 153 can be appropriately changed.

Second Embodiment

In the present embodiment, a structure of a light emitting element andthe optical path length adjusting film which are different from those ofthe first embodiment are explained while referring to FIG. 3 to FIG. 6.In FIG. 3 to FIG. 6, a structure in which one pixel is formed of fourpixels and the four pixels are arranged in a 2×2 square shape isexplained.

FIG. 3 is a diagram showing a part of a pixel arranged in the displayregion 103. In FIG. 3, four pixels, a red pixel 109R, a green pixel109G, and blue pixels 109B1 and 130B2 are shown. Furthermore, in FIG. 3,sections shown as the red pixel 109R, the green pixel 109G, and the bluepixels 109B1, 109B2 are light emitting regions of a light emittingelement. In addition, with respect to the optical path length adjustingfilm, optical path length adjusting films 151, 152 and 153 having highrefractive indices are shown, and an illustration of the optical pathlength adjusting film 154 having the low refractive index is omitted.

In addition, in FIG. 3 to FIG. 6, the film thickness of the optical pathlength adjusting film 151 is set to 20 nm or more and 40 nm or less, thefilm thickness of the optical path length adjusting film 152 is set to50 nm or more and 70 nm or less, and the film thickness of the opticalpath length adjusting film 153 is set to 20 nm or more and 40 nm orless. In the present embodiment, the film thickness of the optical pathlength adjusting film 152 is made thicker than each of the filmthicknesses of the optical path length adjusting film 151 and theoptical path length adjusting film 153. The film thickness of theoptical path length adjusting film 151 is set the same as the filmthickness of the optical path length adjusting film 152.

In addition, since the cross-sectional views of the light emittingelement and the optical path length adjusting film in the dotted lineB1-B2 shown in FIG. 3 to FIG. 6 are the same as the cross-sectionalviews of the light emitting element and the optical path lengthadjusting film shown in FIG. 2, an illustration is omitted.

The optical path length adjusting film 151 is arranged in the pixels109R, 109G, 109B1 and 109B2 as the first pattern. In addition, in thepixel structure shown in FIG. 3, the optical path length adjusting film151 is arranged over the entire surface of the display region 103.Although not shown in the diagrams, at least a part of the optical pathlength adjusting film 151 may overlap the scanning line drive circuit104 shown in FIG. 1.

The optical path length adjusting film 152 is arranged above the opticalpath length adjusting film 151 as the second pattern. In addition, theoptical path length adjusting film 152 is arranged in the pixel 109R andthe pixel 109G. The longitudinal directions of the second optical pathlength adjusting film and the third optical path length adjusting filmare arranged along one direction (y direction).

The optical path length adjusting film 153 is arranged above the opticalpath length adjusting film 151 and the optical path length adjustingfilm 152 as the third pattern. In addition, the optical path lengthadjusting film 153 is arranged in the pixel 109R, and the pixels 109B1and 109B2. The optical path length adjusting film 153 is arranged foreach pixel.

Although an example in which the optical path length adjusting film 153is arranged for each pixel is shown in FIG. 3, one embodiment of thepresent invention is not limited to this example. For example, as shownin FIG. 4, it is possible to be arranged connected to verticallyadjacent pixels. The longitudinal direction of the optical path lengthadjusting film 153 is along a second direction (y direction) orthogonalto the first direction (x direction) in which the scanning line 105connected to the scanning line drive circuit 104 extends. The pixels109B1 and 109B2 overlap, and at least a part of the optical path lengthadjusting film 153 overlaps the pixel 109R in the longitudinal directionof the optical path length adjusting film 153. By adopting a structurein which the optical path length adjusting film 153 extends in thelongitudinal direction of the optical path length adjusting film 153,patterning of the optical path length adjusting film 153 becomes easier,which is preferable.

In addition, as shown in FIG. 5, it is possible to arrange the opticalpath length adjusting film 153 not only vertically adjacent but alsoconnected to pixels adjacent horizontally. That is, the optical pathlength adjusting film 153 can have a shape having an opening in a regionwhich overlaps the green pixel 109G. By forming the optical path lengthadjusting film 153 having an opening in a region which overlaps thegreen pixel 109G, patterning of the optical path length adjusting film153 becomes easier compared with the shape shown in FIG. 4, which ispreferable.

FIG. 6 is a diagram showing a part of a pixel arranged in the displayregion 103. In FIG. 6, four pixels, red pixels 109R1 and 109R2, thegreen pixel 109G, and the blue pixel 109B are shown. In FIG. 6, sectionsshown as the red pixels 109R1, 109R2, the green pixel 109G and the bluepixel 109B are light emitting regions of a light emitting element. Inaddition, with respect to the optical path length adjusting film,optical path length adjusting films 151, 152, and 153 having highrefractive indices are shown, and illustration of the optical pathlength adjusting film 154 having the low refractive index is omitted.

The optical path length adjusting film 151 is arranged in the pixels109R1, 109R2, 109G and 109B as the first pattern. In addition, in thepixel structure shown in FIG. 6, an example is shown in which theoptical path length adjusting film 151 is arranged on the entire surfaceof the display region 103. Although not shown in the diagram, at least apart of the optical path length adjusting film 151 may overlap thescanning line drive circuit 104 shown in FIG. 1.

The optical path length adjusting film 152 is arranged above the opticalpath length adjusting film 151 as the second pattern. In addition, theoptical path length adjusting film 152 is arranged in the pixels 109R1and 109R2 and the pixel 109G.

The optical path length adjusting film 153 is arranged above the opticalpath length adjusting film 151 and the optical path length adjustingfilm 152 as the third pattern. In addition, the optical path lengthadjusting film 153 is arranged in the pixels 109R1 and 109R2 and thepixel 109B.

As explained above, the optical path length adjusting film having thehigh refractive index is divided into three patterns and is arrangedabove light emitting elements of a plurality of colors. In this way,even if the optical path length adjusting film which has the highrefractive index is divided into three patterns for each color so as notto have an optimum film thickness for the light emitting element of eachcolor, it is possible to provide the optical path length adjusting filmhaving the optimum film thickness in a light emitting element of eachcolor. It is possible to obtain a display device having light emittingelements of each color with improved light emitting efficiency.

Third Embodiment

In the present embodiment, a structure of a light emitting element andthe optical path length adjusting film different from those in thesecond embodiment is explained while referring to FIG. 7 to FIG. 9. InFIG. 7 to FIG. 9, a structure in which one pixel is formed by fourpixels and the four pixels are arranged in a square of 2×2 is explained.

FIG. 7 is a diagram showing a part of a pixel arranged in the displayregion 103. In FIG. 7, four pixels, the red pixel 109R, green pixels109G1 and 109G2, and the blue pixel 109B are shown. Here, the red pixel109R and the green pixel 109G1 are arranged along one direction (xdirection). In FIG. 7, sections shown as the red pixel 109R, the greenpixel 109G1, 109G2, and the blue pixel 109B are light emitting regionsof a light emitting element. In addition, with respect to the opticalpath length adjusting film, the optical path length adjusting films 151,152 and 153 which have high refractive indices are shown and anillustration of the optical path length adjusting film 154 which has thelow refractive index is omitted.

Here, in the red pixel 109R, the total thickness of the film thicknessof the optical path length adjusting film 151, the film thickness of theoptical path length adjusting film 152 and the film thickness of theoptical path length adjusting film 153 is t1. In addition, the totalfilm thickness of the optical path length adjusting film 151 and thefilm thickness of the optical path length adjusting film 153 in thegreen pixel 109G1 is t2. In addition, the total film thickness of theoptical path length adjusting film 151 and the film thickness of theoptical path length adjusting film 152 in the green pixel 109G2 is t3.In addition, the film thickness of the optical path length adjustingfilm 151 in the blue pixel 109B is t4. It is preferred to set each ofthe film thicknesses of the optical path length adjusting films 151, 152and 153 so that the relationship between the film thickness t1, the filmthickness t2, the film thickness t3 and the film thickness t4 satisfiest1>t2=t3>t4.

In addition, in FIG. 7 to FIG. 9, the film thickness of the optical pathlength adjusting film 151 is 50 nm or more and 70 nm or less, the filmthickness of the optical path length adjusting film 152 is 20 nm or moreand 40 nm or less, and the film thickness of the optical path lengthadjusting film 153 is 20 nm or more and 40 nm or less. In the presentembodiment, the film thickness of the optical path length adjusting film151 is made thicker than each of the film thicknesses of the opticalpath length adjusting film 152 and the optical path length adjustingfilm 153. In addition, the film thickness of the optical path lengthadjusting film 152 is set to be the same as the film thickness of theoptical path length adjusting film 153.

The optical path length adjusting film 151 is arranged in the pixels109R, 109G1, 109G2 and 109B as the first pattern. In addition, in thepixel structure shown in FIG. 7, the optical path length adjusting film151 is arranged on the entire surface of the display region 103.Although not shown in the diagram, at least a part of the optical pathlength adjusting film 151 may overlap the scanning line drive circuit104 shown in FIG. 1.

The optical path length adjusting film 152 is arranged above the opticalpath length adjusting film 151 as the second pattern. In addition, theoptical path length adjusting film 152 is arranged in the pixels 109Rand 109G2. The optical path length adjusting film 152 is arranged sothat the angle between the longitudinal direction of the optical pathlength adjusting film 152 and one direction (x) of the display region103 is 35° or more and 55° or less.

The optical path length adjusting film 153 is arranged above the opticalpath length adjusting film 151 and the optical path length adjustingfilm 152 as the third pattern. In addition, the optical path lengthadjusting film 153 is arranged in the pixel 109R and the pixel 109G1.The optical path length adjusting film 153 is arranged so that thelongitudinal direction of the optical path length adjusting film 153 isparallel to one direction (x direction) of the display region.

Structure of Light Emitting Element and Optical Path Length AdjustingFilm

Next, a cross-sectional structure of the light emitting element and theoptical path length adjusting film in the dotted line C1-C2 in FIG. 7 isexplained while referring to FIG. 8. FIG. 8 is a cross-sectional view ofthe pixel 109R, the pixels 109G1, 109G2, and the pixel 109B. The pixel109R has a light emitting element 130R, the pixel 109G1 has a lightemitting element 130G1, the pixel 109G2 has a light emitting element130G2, and the pixel 109B has the light emitting element 130B. Inaddition, the light emitting element 130R has the organic layer 127R,the light emitting element 130G1 has an organic layer 127G1, the lightemitting element 130G2 has an organic layer 127G2, and the lightemitting element 130B has the organic layer 127B.

Since the structure shown in FIG. 7 is different from the structureshown in FIG. 2, and the film thickness of the optical path lengthadjusting film 151 and the optical path length adjusting film 152, andthe structure of the pixels 109G1 and 109G2 are only partiallydifferent, only the different parts are explained in detail.

The optical path length adjusting film 151 has a region which overlapswith the light emitting elements 130R, 130G1, 130G2 and 130B. Inaddition, the optical path length adjusting film 152 is arranged abovethe optical path length adjusting film 151 and has a region whichoverlaps with the light emitting element 130R and the light emittingelement 130G2. In addition, the optical path length adjusting film 153is arranged above the optical path length adjusting film 151 and theoptical path length adjusting film 152 and has a region which overlapsthe light emitting element 130R and the light emitting element 130G1.

The optical path length adjusting film 154 which has the low refractiveindex is arranged above the optical path length adjusting films 151, 152and 153 which have the high refractive index. The optical path lengthadjusting film 154 is arranged in common with the pixels 109R, 109G and109B.

In FIG. 8, although an example in which the optical path lengthadjusting films 151, 152 and 153 having the high refractive index arestacked in this order is shown, an embodiment of the present inventionis not limited to this example. The stacking order of the optical pathlength adjusting films 151, 152 and 153 can be appropriately changed.

Next, a structure different from the arrangement of pixels arranged inthe display region 103 shown in FIG. 7 is explained while referring toFIG. 9. In FIG. 9, in a pixel, the direction in which one side of alight emitting region extends is arranged so as to intersect a firstdirection in which the scanning line 105 connected to the scanning linedrive circuit 104 extends.

The optical path length adjusting film 151 is arranged in the pixels109R, 109G1, 109G2 and 109B as the first pattern. In addition, in thepixel structure shown in FIG. 9, the optical path length adjusting film151 is arranged over the entire surface of the display region 103.Although not shown in the diagram, at least a part of the optical pathlength adjusting film 151 may overlap the scanning line drive circuit104 shown in FIG. 1.

The optical path length adjusting film 152 is arranged over the opticalpath length adjusting film 151 as the second pattern. In addition, theoptical path length adjusting film 152 is arranged in the pixel 109R andthe pixel 109G1. The optical path length adjusting film 152 is arrangedso that the angle formed by the longitudinal direction of the opticalpath length adjusting film 152 and one direction (x direction) of thedisplay region 103 is 35° or more and 55° or less.

The optical path length adjusting film 153 is arranged over the opticalpath length adjusting film 151 and the optical path length adjustingfilm 152 as the third pattern. In addition, the optical path lengthadjusting film 153 is arranged in the pixels 109R and 109G2. The opticalpath length adjusting film 153 is arranged so that the angle between thelongitudinal direction of the optical path length adjusting film 153 andone direction (x direction) of the display region 103 is 35° or more and55° or less. In addition, the longitudinal direction of the optical pathlength adjusting film 153 and the longitudinal direction of the opticalpath length adjusting film 152 intersect each other, and the opticalpath length adjusting film 153 and the optical path length adjustingfilm 152 overlap each other above the pixel 109R.

As explained above, the optical path length adjusting film which has thehigh refractive index is divided into three patterns and is arrangedabove light emitting elements of a plurality of colors. In this way,even if the optical path length adjusting film having the highrefractive index is divided into three patterns for each color so as notto have an optimum film thickness for the light emitting element of eachcolor, it is possible to arrange the optical path length adjusting filmhaving the optimum film thickness in a light emitting element of eachcolor. A display device can be obtained with light emitting elements ofeach color with improved light emitting efficiency.

Manufacturing Method of Display Device

A method of manufacturing a display device according to one embodimentof the present invention is explained while referring to FIG. 10 to FIG.13. FIG. 10 to FIG. 13 are diagrams showing a structure of across-section cut along the line A1-A2 of the display region 103 shownin FIG. 1. FIG. 10 to FIG. 13 show cross sections of three pixels 109R,109G and 109B as a part of the display region 103.

As shown in FIG. 10, a first substrate 101 and a second substrate 112are used in the display device 100. A glass substrate, a quartzsubstrate, or a flexible substrate (polyimide, polyethyleneterephthalate, polyethylene naphthalate, triacetyl cellulose, cyclicolefin copolymer, cycloolefin polymer, other resin substrate havingflexibility) can be used as the first substrate 101 and the secondsubstrate 112. In the case when it is not necessary for the firstsubstrate 101 and the second substrate 112 to have translucency, it isalso possible to use a metal substrate, a ceramic substrate or asemiconductor substrate. In the present embodiment, polyimide is used asthe first substrate 101 and polyethylene terephthalate is used as thesecond substrate 112.

An underlying layer 113 is formed above the first substrate 101. Theunderlying layer 113 is an insulating layer made of an inorganicmaterial such as silicon oxide, silicon nitride or aluminum oxide or thelike. The underlying layer 113 is not limited to a single layer and mayhave a stacked laminated structure in which, for example, a siliconoxide layer and a silicon nitride layer are combined. This structure maybe appropriately determined considering adhesion to the first substrate101 and gas barrier properties to a transistor 120 described later.

A transistor 120 is formed above the underlying layer 113. The structureof the transistor 120 may be a top gate type or a bottom gate type. Inthe present embodiment, the transistor 120 includes a semiconductorlayer 114 arranged above the underlying layer 113, a gate insulatingfilm 115 covering the semiconductor layer 114, and a gate electrode 116arranged above the gate insulating film 115. In addition, an interlayerinsulating layer 122 which covers the gate electrode 116 is arrangedabove the transistor 120. Source or drain electrodes 117 and 118 arearranged above the interlayer insulating layer 122. Source or drainelectrodes 117 and 118 are respectively connected to the semiconductorlayer 114. Furthermore, although an example in which the interlayerinsulating layer 122 has a single layer structure is explained in thepresent embodiment, the interlayer insulating layer 122 may also have astacked structure.

Furthermore, the material of each layer forming the transistor 120 maybe any known material and is not particularly limited. For example,generally, polysilicon, amorphous silicon or an oxide semiconductor canbe used as the semiconductor layer 114. Silicon oxide or silicon nitridecan be used as the gate insulating film 115. The gate electrode 116 ismade of a metal material such as copper, molybdenum, tantalum, tungstenor aluminum. Silicon oxide or silicon nitride can be used as theinterlayer insulating layer 122. The source or drain electrode 117 andthe source or drain electrode 118 are each made of a metal material suchas copper, titanium, molybdenum or aluminum.

Although not shown in FIG. 10, it is possible to arrange a first wiringmade of the same metal material as the metal material forming the gateelectrode 116 in the same layer as the gate electrode 116. The firstwiring can be arranged as, for example, a scanning line driven by thescanning line drive circuit 104 or the like. Although not shown in FIG.10, a second wiring extending in a direction which intersects the firstwiring can be arranged in the same layer as the source or drainelectrode 117 and the source or drain electrode 118. The second wiringcan be arranged, for example, as a data line driven by the data linedrive circuit or the like.

A planarization film 123 is formed above the transistor 120. Theplanarization film 123 is formed including an organic resin material.For example, known organic resin materials such as polyimide, polyamide,acrylic, epoxy and the like can be used as the organic resin material.These materials are capable of forming a film by a solution coatingmethod and are characterized by a high flattening effect. Although notspecifically shown, the planarization film 123 is not limited to asingle layer structure, and may have a stacked layer structure of alayer containing an organic resin material and an inorganic insulatinglayer.

A contact hole which exposes a part of the source or drain electrode 118is formed in the planarization film 123. The contact hole is an aperturepart for electrically connecting a pixel electrode 125 described laterand the source or drain electrode 118. Therefore, the contact hole isarranged so as to overlap a part of the source electrode or the drainelectrode 118. The source or drain electrode 118 is exposed at thebottom surface of the contact hole.

A protective film 124 is formed above the planarization film 123. Theprotective film 124 overlaps the contact hole formed in theplanarization film 123. The protective film 124 is preferred to have abarrier function against moisture and oxygen, and is formed using, forexample, an inorganic insulating material such as a silicon nitride oraluminum oxide.

A pixel electrode 125 is formed above the protective film 124. The pixelelectrode 125 is electrically connected to the source electrode or thedrain electrode 118 via a contact hole arranged in the protective film124 and the planarization film 123. In the display device 100 of thepresent embodiment, the pixel electrode 125 functions as an anode whichforms the light emitting element 130. The pixel electrode 125 has adifferent structure depending on whether it is a top emission type or abottom emission type. For example, in the case of a top emission type,either a metal film having a high reflectance is used as the pixelelectrode 125, or a stacked structure of a transparent conductive filmhaving a high work function such as an indium oxide based transparentconductive layer (for example, ITO) or zinc oxide based transparentconductive (for example, IZO, ZnO) and a metal film is used as shown inFIG. 2 and FIG. 8. On the other hand, in the case of a bottom emissiontype, the transparent conductive layer described above is used as thepixel electrode 125. In the present embodiment, a top emission typeorganic EL display device is explained as an example.

A first insulating layer 126 made of an organic resin material is formedabove the pixel electrode 125. A known resin material such as polyimide,polyamide, acrylic, epoxy or siloxane can be used as the organic resinmaterial. The first insulating layer 126 has an aperture part in a partabove the pixel electrode 125. The first insulating layer 126 isarranged to cover an end part (edge part) of the pixel electrode 125between adjacent pixel electrodes 125, and functions as a member whichseparates adjacent pixel electrodes 125. Therefore, the first insulatinglayer 126 is also generally referred to as a “partition wall” or “bank”.A part of the pixel electrode 125 exposed from the first insulatinglayer 126 is a light emitting region of the light emitting element 130.It is preferred that the inner wall of the aperture part of the firstinsulating layer 126 has a tapered shape. In this way, it is possible toreduce coverage defects at the end part of the pixel electrode 125 whenforming a light emitting layer described later. The first insulatinglayer 126 may not only cover the end part of the pixel electrode 125 butalso function as a filling material which fills a concave part caused bythe contact hole of the planarization film 123 and the protective film124.

An organic layer 127 is formed above the pixel electrode 125. Theorganic layer 127 has at least a light emitting layer formed from anorganic material and functions as a light emitting part of the lightemitting element 130. In addition to the light emitting layer, theorganic layer 127 includes various layers such as a hole injection layerand/or hole transport layer, an electron injection layer and/or electrontransport layer explained in FIG. 2 and FIG. 8. The organic layer 127 isarranged to cover the light emitting region, that is, to cover theaperture part of the first insulating layer 126 in the light emittingregion.

Furthermore, in the present embodiment, by arranging the organic layer127 including a light emitting layer which emits light of a desiredcolor, and forming an organic layer 127 including different lightemitting layers above each pixel electrode 125, a structure is obtainedin which each color of RGB is displayed. That is, in the presentembodiment, the light emitting layer of the organic layer isdiscontinuous between adjacent pixel electrodes 125. A known structureor a known material can be used as the organic layer 127 and is notparticularly limited to the structure of this embodiment.

The counter electrode 128 is formed above the organic layer 127 and thefirst insulating layer 126. The counter electrode 128 functions as acathode forming the light emitting element 130. Since the display device100 of the present embodiment is a top emission type, a transparentelectrode is used as the counter electrode 128. An MgAg thin film or atransparent conductive layer (ITO or IZO) is used as the thin filmforming the transparent electrode. The counter electrode 128 is alsoarranged above the first insulating layer 126 so as to bridge across thepixels 109R, 109G and 109B. The counter electrode 128 is electricallyconnected to an external terminal via a lower conductive layer in aperiphery region near the end of the display region 103. As describedabove, in the present embodiment, the light emitting element 130 isformed by a part (anode) of the pixel electrode 125 exposed from thefirst insulating layer 126, the organic layer (light emitting part) andthe counter electrode 128 (cathode).

Next, as shown in FIG. 11, in the pixels 109R, 109G and 109B, theoptical path length adjusting films 151, 152 and 153 having the highrefractive index and the optical path length adjusting film 154 havingthe low refractive index are formed above each light emitting element.

The optical path length adjusting film 151 is formed above the lightemitting element 130R, the light emitting element 130G and the lightemitting element 130B, the optical path length adjusting film 152 isformed above the light emitting element 130R and the light emittingelement 130G, and the optical path length adjusting film 153 is formedabove the light emitting element 130R and the light emitting element130B. In addition, the optical path length adjusting film 154 is formedabove the light emitting element 130R, the light emitting element 130Gand the light emitting element 130B.

For example, it is possible to use a general organic material or atransparent oxide such as ITO as the optical path length adjusting films151, 152 and 153. The refractive indexes of the optical path lengthadjusting films 151, 152 and 153 are preferably, for example, 1.6 to2.6. The optical path length adjusting films 151, 152 and 153 arearranged using a material having the same refractive index. In addition,it is preferred that the optical path length adjusting films 151, 152and 153 are formed of the same material.

In addition, the film thickness of the optical path length adjustingfilm 151 is 20 nm or more and 40 nm or less, the film thickness of theoptical path length adjusting film 152 is 50 nm or more and 70 nm orless, and the film thickness of the optical path length adjusting film153 is 20 nm or more and 40 nm or less. The film thickness of theoptical path length adjusting film 152 is larger than each of the filmthicknesses of the optical path length adjusting film 151 and theoptical path length adjusting film 153, and the film thicknesses of theoptical path length adjusting film 151 and the optical path lengthadjusting film 153 are preferably the same.

In addition, for example, fluoride such as LiF or silicon oxide and thelike can be used as the optical path length adjusting film 154. Therefractive index of the optical path length adjusting film is preferably1.0 to 1.5 for example. The film thickness of the optical path lengthadjusting film 154 is 30 nm or more and 120 nm or less.

As shown in FIG. 12, a first inorganic insulating layer 131, an organicinsulating layer 132, and a second inorganic insulating layer 133 areformed above the display region 103. The first inorganic insulatinglayer 131, the organic insulating layer 132 and the second inorganicinsulating layer 133 function as a sealing film for preventing moistureand oxygen from entering the light emitting element 130. By arranging asealing film above the display region 103, it is possible to preventmoisture and oxygen from entering the light emitting element 130, and itis possible to improve the reliability of the display device. A film ofsilicon nitride (Si_(x)N_(y)), silicon oxynitride (SiO_(x)N_(y)),silicon nitride oxide (SiN_(x)O_(y)), aluminum oxide (Al_(x)O_(y)),aluminum nitride (Al_(x)N_(y)), aluminum nitride (Al_(x)O_(y)N_(z))),aluminum nitride oxide (Al_(x)N_(y)O_(z)) or the like can be used as thefirst inorganic insulating layer 131 and the second inorganic insulatinglayer 133 (x, y, z are arbitrary). A polyimide resin, an acrylic resin,an epoxy resin, a silicone resin, a fluororesin and a siloxane resin orthe like can be used as the organic insulating layer 132.

As shown in FIG. 13, the counter substrate 102 is bonded above thesecond inorganic insulating layer 133 by an adhesive material 135. Forexample, an acrylic type, rubber type, silicone type or urethane typeadhesive material can be used as the adhesive material 135. In addition,the adhesive material 135 may contain moisture absorbing substances suchas calcium and zeolite. By containing a moisture absorbing substance inthe adhesive material 135, even when moisture enters into the displaydevice 100, it is possible to delay the arrival of moisture to the lightemitting element 130. In addition, a spacer may be arranged on theadhesive material 135 in order to secure a gap between the firstsubstrate 101 and the counter substrate 102. This spacer may be mixedwith the adhesive material 135 or may be formed of a resin or the likeon the first substrate 101. In addition, the same material as thematerials exemplified for the first substrate 101 and the secondsubstrate 112 can be used as the counter substrate 102.

For example, an overcoat layer may be arranged on the counter substrate102 for flattening. In the case when an organic layer emits white light,a color filter corresponding to each RGB color and a black matrixarranged between the color filters may be arranged on a main surface(surface facing the first substrate 101) on the counter substrate 102.In the case when a color filter is not formed on the counter substrate102 side, for example, a color filter may be directly formed on thesealing film and the adhesive 135 may be formed thereon. A polarizationplate 138 is arranged on the rear surface (display surface side) of thecounter substrate 102.

As explained above, a structure is obtained in which the optical pathlength adjusting film having the high refractive index is divided intothree patterns and arranged above light emitting elements of a pluralityof colors. In this way, even if the optical path length adjusting filmis divided into three patterns for each color and an optimum filmthickness for the light emitting elements of each color is not provided,it is possible to arrange the optical path length adjusting film havingthe optimum film thickness for light emitting elements of each color.

In addition, as shown in the present embodiment, by arranging theoptical path length adjusting films divided into three patterns abovethe light emitting elements of a plurality of colors, it is possible toform the optical path length adjusting film having an optimum filmthickness for each color even when a pixel unit mask is not used. Inthis way, it is possible to expand the process margin of the displaydevice. That is, it is possible to provide a manufacturing method of adisplay device with an expanded process margin while maintaining thesame characteristics as in the case where the optical path lengthadjusting films having different film thicknesses are separately coatedfor each light emitting element of each color.

What is claimed is:
 1. A manufacturing method of a display device, themethod comprising: forming a first pixel electrode, a second pixelelectrode, and a third pixel electrode above a substrate; forming afirst organic layer of a first color above the first pixel electrode, asecond organic layer of a second color above the second pixel electrode,a third organic layer of a third color above the third pixel electrode;forming a counter electrode above the first organic layer, the secondorganic layer, and the third organic layer; forming a first optical pathlength adjustment film on the counter electrode overlapping the firstorganic layer, the second organic layer and the third organic layer;forming a second optical path length adjustment film on the firstoptical path length adjustment film overlapping the first organic layerand the second organic layer; and forming a third optical path lengthadjustment film in contact with the second optical path lengthadjustment film overlapping the first organic layer and in contact withthe first optical path length adjustment film overlapping the thirdorganic layer.
 2. The method according to claim 1, wherein a filmthickness of the second optical path length adjustment film is formedthicker than a film thickness of the first optical path lengthadjustment film and a film thickness of the third optical path lengthadjustment film, respectively.
 3. The method according to claim 1,wherein a film thickness of the first optical path length adjustmentfilm is formed the same as a film thickness of the third optical pathlength adjustment film.
 4. The method according to claim 1, wherein afirst refractive index of the first optical path length adjustment film,a second refractive index of the second optical path length adjustmentfilm, and a third refractive index of the third optical path lengthadjustment film are the same.
 5. The method according to claim 1,wherein a film thickness of the first optical path length adjustmentfilm is formed thicker than a film thickness of the second optical pathlength adjustment film and a film thickness of the third optical pathlength adjustment film, respectively.
 6. The method according to claim1, wherein a film thickness of the second optical path length adjustmentfilm is formed the same as a film thickness of the third optical pathlength adjustment film.
 7. The method according to claim 1, the methodfurther comprising: forming a fourth optical path length adjustment filmin contact with the second optical path length adjustment film and thethird optical path length adjustment film, and a fourth refractive indexof the fourth optical path length adjustment film is lower than thefirst refractive index, the second refractive index, and the thirdrefractive index, respectively.
 8. The method according to claim 7, themethod further comprising: forming a sealing film above the fourthoptical path length adjustment film.
 9. The method according to claim 1,wherein the first optical path length adjustment film is formed on theentire surface of the substrate.